This type of motor with reduction gear mechanism utilized as a wiper motor contains a motor shaft supported to allow free rotation in a motor case and a gear case; a pair of worms formed in the vicinity of one end of the motor shaft within the gear case and with mutually opposite screw torsion directions; a pair of counter gears disposed on both sides of the motor shaft, and including large-diameter gears meshing with the worms respectively, and small-diameter gears having the same axis as the large-diameter gear to rotate as one piece; and an output gear meshing with each small-diameter gear of the pair of counter gears (For example, see the patent document 1)
This wiper motor contains a two-stage reduction gear mechanism in which a pair of counter gears mesh with a pair of worms formed with mutually opposite screw torsion directions. Therefore, the direction of the thrust load generated by the combination of one of worms and counter gear becomes opposite to the direction of the thrust load generated by the combination of the other of worms and counter gear so that the thrust loads are cancelled out. Thus, along with making a high-accuracy and strong thrust bearing unnecessary, the play in the motor shaft is eliminated and the wiper motor rotation is smooth.
Patent document 1: Japanese Patent Non-examined Publication No. 9-175334